Polygonum Genus [herbs] knotweed; smartweed Polygonaceae

Polygonum hydropiperwww.fungoceva.it

Polygonum hydropiper.www.fungoceva.it. (Accessed 11/2014).

Polygonum is a genus annual or perennial herbs (ours) and vines. Stipules consist of a membranous sheath below each leaf (ocreae), the upper margins are often bristly. 

Leaves usually alternate, simple (1-parted), margins smooth (entire). 

Flowers small, petals and sepals alike (tepals). Ovary attached above tepals (superior). 

Fruit consists of developed seed (achene), flat or 3-sided. 

Polygonum cespitosum.Bobby Hattaway.www.discoverlife.org

Polygonum caespitosum.ocreae.Bobby Hattaway.www.discoverlife.org. (Accessed 4/2014).